Nanoporous TiO₂-Based Distributed Bragg Reflectors for Near-Infrared Wavelength Applications

Guan, Xiang-Yu,Leem, Jung Woo,Yu, Jae Su American Scientific Publishers 2015 Journal of Nanoscience and Nanotechnology Vol.15 No.12

경사입사각증착법을 이용한 이산화 티타늄 박막 기반의 고반사 분포 브래그 반사기 제작 및 특성

Xiang-Yu Guan,임정우,정관수,유재수 한국진공학회 2014 한국진공학회 학술발표회초록집 Vol.2014 No.2

Fabrication and analysis of highly-reflective metal-dielectric mirrors for high-performance semiconductor laser applications

Xiang-Yu Guan,임정우,이수현,장호진,김정호,한수욱,유재수 한국물리학회 2016 Current Applied Physics Vol.16 No.2

The device performance improvement of ridge waveguide (RWG) laser diodes (LDs), operating at a wavelength (l) of ~960 nm, with a metal-dielectric high-reflection (HR) mirror consisting of Au/TieSiO2 layers on the back facet was demonstrated. To determine the optimum thickness of each layer, optical reflection calculations were performed using a rigorous coupled-wave analysis method, which leads to the resultant Au (80 nm)/Ti (5 nm)eSiO2 (164 nm) layers. The layers exhibited a broad high reflection band of >91% over a wavelength range of 920e1000 nm, indicating the reflectivity of ~91.2% at l ~ 960 nm. For 2 mm-cavity RWG LDs with the Au/TieSiO2 HR mirror, an enhanced maximum output power (Pmax) of 499.3 mW at an injection current of 3000 mA and a decreased threshold current (Ith) of 516 mA (i.e., Pmax ¼ 259.4 mW and Ith ¼ 650 mA for the uncoated LDs) were obtained, showing an increased slope efficiency percentage of 82%. The external differential quantum efficiency was also increased from ~17.1 to ~31.1%. Also, the full widths at half maximum values of beam divergences of the device were 38 (vertical direction) and 4 (horizontal direction).

Broadband high-reflective distributed Bragg reflectors based on amorphous silicon films for semiconductor laser facet coatings.

Guan, Xiang-Yu,Leem, Jung Woo,Lee, Soo Hyun,Jang, Ho-Jin,Kim, Jeong-Ho,Hann, Swook,Yu, Jae Su Optical Society of America 2015 Applied Optics Vol.54 No.5

<P>We fabricated amorphous silicon (a-Si)-based distributed Bragg reflectors (DBRs) consisting of alternating dense/porous films (i.e., pair) for a center wavelength (λ(c)) of 0.96 μm by oblique angle deposition (OAD) technique using an electron-beam evaporation system. The dense (high refractive index, i.e., high-n) and porous (low-n) a-Si films were deposited at two incident vapor flux angles of 0 and 80 in the OAD, respectively. Their optical reflectance characteristics were investigated in the wavelength range of 0.6-1.5 μm, including theoretical comparison using a rigorous coupled-wave analysis method. Above three pairs, the reflectivity (R) of a-Si DBRs was almost saturated at wavelengths around 0.96 μm, exhibiting R values of >97%. For the a-Si DBR with only three pairs, a broad normalized stop bandwidth (δλ/λ(c)) of 22.5% was obtained at wavelengths of 0.87-1.085??μm, keeping high R values of >95%. To simply demonstrate the feasibility of device applications, the a-Si DBR with three pairs was coated as a high-reflection layer at the rear facet of GaAs/InGaAs quantum-well laser diodes (LDs) operating at λ=0.96??μm. For the LDs coated with three-pair a-Si DBR, external differential quantum efficiency (η(d)) was nearly doubled compared to the uncoated LDs, indicating the η(d) value of 50.6% (i.e., η(d)25.5% for the uncoated LDs).</P>

Production of 1,5-Dihydroxy-3-Methoxy-7-Methylanthracene-9,10-Dione by Submerged Culture of Shiraia bambusicola

( Yu Jie Cai ),( Yan Rui Ding ),( Guan Jun Tao ),( Xiang Ru Liao ) 한국미생물 · 생명공학회 2008 Journal of microbiology and biotechnology Vol.18 No.2

DC-Link Voltage Balance Control in Three-phase Four-wire Active Power Filters

Yu Wang,Yuanpeng Guan,Yunxiang Xie,Xiang Liu 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.5

The three-phase four-wire shunt active power filter (APF) is an effective method to solve the harmonic problem in three-phase four-wire power systems. In addition, it has two possible topologies, a four-leg inverter and a three-leg inverter with a split-capacitor. There are some studies investigating DC-link voltage control in three-phase four-wire APFs. However, when compared to the four-leg inverter topology, maintaining the balance between the DC-link upper and lower capacitor voltages becomes a unique problem in the three-leg inverter with a split-capacitor topology, and previous studies seldom pay attention to this fact. In this paper, the influence of the balance between the two DC-link voltages on the compensation performance, and the influence of the voltage balance controller on the compensation performance, are analyzed. To achieve the balance between the two DC-link capacitor voltages, and to avoid the adverse effect the voltage balance controller has on the APF compensation performance, a new DC-link voltage balance control strategy for the three-phase four-wire split-capacitor APF is proposed. Representative simulation and experimental results are presented to verify the analysis and the proposed DC-link voltage balance control strategy.

A review of source tracking techniques for fine sediment within a catchment

Guan, Zhuo,Tang, Xiang-Yu,Yang, Jae E.,Ok, Yong Sik,Xu, Zhihong,Nishimura, Taku,Reid, Brian J. Springer-Verlag 2017 Environmental geochemistry and health Vol.39 No.6

<P>Excessive transport of fine sediment, and its associated pollutants, can cause detrimental impacts in aquatic environments. It is therefore important to perform accurate sediment source apportionment to identify hot spots of soil erosion. Various tracers have been adopted, often in combination, to identify sediment source type and its spatial origin; these include fallout radionuclides, geochemical tracers, mineral magnetic properties and bulk and compound-specific stable isotopes. In this review, the applicability of these techniques to particular settings and their advantages and limitations are reviewed. By synthesizing existing approaches, that make use of multiple tracers in combination with measured changes of channel geomorphological attributes, an integrated analysis of tracer profiles in deposited sediments in lakes and reservoirs can be made. Through a multi-scale approach for fine sediment tracking, temporal changes in soil erosion and sediment load can be reconstructed and the consequences of changing catchment practices evaluated. We recommend that long-term, as well as short-term, monitoring of riverine fine sediment and corresponding surface and subsurface sources at nested sites within a catchment are essential. Such monitoring will inform the development and validation of models for predicting dynamics of fine sediment transport as a function of hydro-climatic and geomorphological controls. We highlight that the need for monitoring is particularly important for hilly catchments with complex and changing land use. We recommend that research should be prioritized for sloping farmland-dominated catchments.</P>

Effect of Device Package on Optical, Spectral, and Thermal Properties of InGaN/GaN Near-Ultraviolet Lateral Light-Emitting Diodes

이수현,Xiang-Yu Guan,전수건,유재수 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.71 No.6

We investigated the package effect on the temperature-dependent optical and spectral characteristics of InGaN/GaN near-ultraviolet (NUV) lateral light-emitting diodes (LLEDs) on the metal heatsink (MH) and package (PKG) in the injection current range of 0 - 500 mA at 298 and 358 K. For the NUV LLEDs on the MH, the device characteristics reflected directly its chip performance. For the NUV LLEDs on the PKG, the rapidly varied spectral shift as well as the reduced device efficiency was observed due to the increased number of layers with relatively low thermal conductivities. The junction temperature (Tj) and thermal resistance of the NUV LLEDs on the PKG were also significantly increased compared to the NUV LLEDs on the MH. The three-dimensional heat transfer simulations for both the devices were carried out to obtain the temperature distributions by finite element method. The theoretically calculated Tj values showed a good agreement with the experimentally measured Tj values.

A Study between the Internal Control and Tax Risk -Based on the Listed Real Estate Enterprises in China-

Li Xiang-Yu(이상우),Kim Pyoung-Ki(김평기),Wu Guan-Zheng(오관정) 한국국제회계학회 2019 국제회계연구 Vol.0 No.88

2009년 5월에 중국 세무총국은 기업에서 세무리스크 관리 시스템을 구축할 수 있도록 돕기 위해〈대기업의 세무리스크 관리지침〉(2009)을 발표하였다. 이번에 처음 세무리스크에 대해 공식적으로 별도 제시되어 학술계에서 큰 반향을 유발하였다. 세무리스크는 기업이 직면한 재무리스크중에 하나이며 그 효과를 무시할 수 없다. 부적절한 취급 또는 경미한 태만은 경제적 손실, 평판의 손상 및 심지어 파산위기를 초래 할 수 있다. 대부분 기업에서 부적절한 내부통제 시스템으로 인한 세금리스크 관리능력이 제한되기 때문에 중국에서 세금리스크 관리가 이미 시작되었다. 이는 경영 실적에 영향을 미치고 이익을 보장하는 중요한 요소이며 세무리스크를 통제하고 감소하는 것은 기업의 생존과 발전에 중요한 결정 요소이다. 본 연구는 내부통제 이론을 기반으로 경영 품질, 보고품질 및 규정준수 품질의 관점에서 연구를 진행하고자 한다. 2013년부터 2017년까지 중국 A주 부동산업 90개 상장기업을 연구대상으로 삼고 세무리스크에 관한 가설을 제시하였다. 연속 5년간의 450개 표본 데이터를 가져와 회귀 분석을 하였다. 분석결과에 따라 경영 품질은 10% 수준에서 유의한 양(+)상관관계가 나타났다. 보고 품질은 5% 수준에서 유의한 음(-) 상관관계가 나타났다. 규정준수 품질은 10% 수준에서 유의한 음(-) 상관관계가 나타났다. 마지막으로, 기업의 세무리스크와 내부통제를 실현의 각도에 대한 상관관계를 분석하고 세무리스크를 통제하고 감소하기 위해 합리적인 제안을 제시하였다. 이 연구결과는 기업이 전략 계획을 수립하고 리스크를 예방할 수 있는 참고를 제공하였다. In May 2009, the State Administration of Taxation issued the “Guidelines for the Management of tax risk of Large Enterprises”(2009) to help enterprises establish a tax risk management system. This is the first time that tax risk have been formally presented in a separate form, causing a stir in the academic and practical circles. Tax risk is one of the financial risks faced by enterprises. The consequences can not be underestimated. Improper handling or slight neglect may bring economic losses, reputation damage and even bankruptcy crisis. At present, the tax risk management of Chinese enterprises has just started. Many enterprises have inadequate internal control systems and limited ability to manage tax risk. Tax risk have become an important factor affecting business results and safeguarding corporate interests. The control and reduction of risks is crucial to the survival and development of enterprises. This paper cuts through the internal control of the enterprise, and selects 90 enterprises during 2013-2017 for the total of 450 samples in the A-share real estate industry listed in China"s securities market as the research object. Combined with the theory of internal control and from the perspectives of operation, reporting and compliance with taxation the hypothesis is proposed and regression models are constructed. The empirical study is related to the correlation between the degree of implementation of internal control and corporate tax risk, and finds that The quality of the operation is positively correlated with the tax risk of the enterprise in the level of 10%. The quality of the report is negatively correlated with the tax risk of the enterprise in the level of 5%. The quality of compliance is negatively correlated with the tax risk of the enterprise in the level of 10%. Finally, the paper puts forward reasonable suggestions for the reduction and prevention of tax risk. The study results provide references for enterprises to make strategic plans and prevent risks.

DC-Link Voltage Balance Control in Three-phase Four-wire Active Power Filters

Wang, Yu,Guan, Yuanpeng,Xie, Yunxiang,Liu, Xiang The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.5

The three-phase four-wire shunt active power filter (APF) is an effective method to solve the harmonic problem in three-phase four-wire power systems. In addition, it has two possible topologies, a four-leg inverter and a three-leg inverter with a split-capacitor. There are some studies investigating DC-link voltage control in three-phase four-wire APFs. However, when compared to the four-leg inverter topology, maintaining the balance between the DC-link upper and lower capacitor voltages becomes a unique problem in the three-leg inverter with a split-capacitor topology, and previous studies seldom pay attention to this fact. In this paper, the influence of the balance between the two DC-link voltages on the compensation performance, and the influence of the voltage balance controller on the compensation performance, are analyzed. To achieve the balance between the two DC-link capacitor voltages, and to avoid the adverse effect the voltage balance controller has on the APF compensation performance, a new DC-link voltage balance control strategy for the three-phase four-wire split-capacitor APF is proposed. Representative simulation and experimental results are presented to verify the analysis and the proposed DC-link voltage balance control strategy.